Segment Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) Segment	Dec. 31, 2016 USD ($) Segment	Dec. 31, 2015 USD ($)
Segment Information [Abstract]
Number of reportable segments | Segment									1	2
Revenues [Abstract]
Net premiums earned	$ 97,075	$ 89,100	$ 67,996	$ 73,974	$ 69,141	$ 71,235	$ 68,726	$ 66,909	$ 328,145	$ 276,011	$ 263,335
Net investment income	5,661	4,027	4,716	3,692	3,982	3,513	3,549	3,440	18,095	14,483	12,498
Commissions and other income									5,308	5,275	5,703
Net realized gains (losses) on investments	$ 4,152	$ 5,944	$ 3,296	$ 6,294	$ 6,204	$ 7,732	$ 280	$ 9,012	19,686	23,228	(1,261)
Total revenues									371,234	318,997	280,275
Property and Casualty Insurance [Member]
Revenues [Abstract]
Net premiums earned									328,145	276,011	263,335
Net investment income									18,095	14,483	12,498
Commissions and other income									5,308	5,275	5,703
Net realized gains (losses) on investments									19,686	23,228	(1,261)
Total revenues									$ 371,234	$ 318,997	$ 280,275